17.6 Patching Programs

By default, GDB opens the file containing your program’s
executable code (or the corefile) read-only. This prevents accidental
alterations to machine code; but it also prevents you from intentionally
patching your program’s binary.

If you’d like to be able to patch the binary, you can specify that
explicitly with the set write command. For example, you might
want to turn on internal debugging flags, or even to make emergency
repairs.

set write on

set write off

If you specify ‘set write on’, GDB opens executable and
core files for both reading and writing; if you specify set write
off (the default), GDB opens them read-only.

If you have already loaded a file, you must load it again (using the
exec-file or core-file command) after changing set
write, for your new setting to take effect.

show write

Display whether executable files and core files are opened for writing
as well as reading.